In prior art devices for supersonic wave diagnosing internal organs within a body cavity by combining a supersonic wave probe means transmitting and receiving supersonic waves and an endoscope for observing the interior of the body cavity with each other, the field of vision of the above mentioned endoscope is blocked by the supersonic wave probe means, the position in which the tip of the supersonic wave probe transmitting and receiving supersonic waves is to be contacted with an internal organ can not be sighted, the tip of the above mentioned supersonic wave probe can not be observed and, as a result, in what position the tip of the supersonic wave probe is in contact with the internal organ can not be confirmed. Therefore, the body cavity interior supersonic wave diagnosing device of the present invention makes it possible to sight with an endoscope the tip of a supersonic wave probe having a window for transmitting and receiving supersonic waves.